Flex vs. stiffness?

[ghcoe]

So in a attempt to sell a foamie I found that the hardest part of the sale is the construction method. They are really interested, because it weighs so little, but once you describe the construction method the conversation ends and you never see them again.

I had originally designed #2 to be simple and easy to build. Just to see how simple and cheap I can get . This build also showed me just how ridged the box could be. During construction I thought to myself this would probably also be a great off road build. My intent after selling this one was to pursue that route with #3.

Well things did not work out like I had hoped, with plenty of interest, but no purchases because of the lack of knowledge in the main stream public on foamies. So came about my YouTube channel showing people how I built my #2 in hopes of stirring up awareness. Awareness is one thing, but proof of concept is another. You have to sell people on a construction type not commonly known. So my channel has also steered to a foamie in actual use. Not driving down a road like a normal trailer, but showing a foamie being used off road. The theory is this, it is more convincing to the average Joe seeing a unknown construction being used harder than they would use it.

So since #2 did not sell and I was stuck with it I figured lets go with my idea of building a off road foamie .

#2 is quite ridged and had originally just sat on the frame. I found that over the winter that the area between the trailer floor and the trailer was a moisture trap. Also, with the limited towing that I had done with the trailer, the canvas/paint weave acted like sandpaper against the frame paint. This cause rust to form and I had visible rust stains beginning g to show under the trailer. So the next step was to lift the trailer off the frame and add GPW's recommended drip rail. So I purchased some 1"x2"'s and lifted the floor 3/4" and added sheet rock edging strips around the perimeter of the trailer. This was just before this trip....



Go to 3:40 of the video, at the point I was airing down for the dirt road surfaces. I had air down from 20psi to 12psi. Also, I had flipped the bottom two springs in the spring pack to lighten the spring rate, so essentially I only have the main spring as a working spring at this time. Stock 12" tires/wheels are being used in this video.

Watching the video you will see the trailer taking some hard blows and bounces. I was trying to hit some bumps hard on purpose to see how the trailer would fair. I some points I feel I over did it a bit, it was easy to do with those small skinny tires though.

After this trip I inspected the trailer for structural damage. I found that at the points where the 1"x2"'s, that I used to lift the floor off the frame, the canvas had delaminated. In most cases the delamination reached about 2" out and up at those points. Some a bit worse and some not at all. A simple fix, but I had to figure out how to prevent this from happening again. After watching my video I could see better the hammering the trailer took and figured that the violent side to side motion was creating enough force to compress the foam and therefore cause the delamination at the support locations. Probably not a concern on normal roads, but a concern for me. The fix to me was two options, more floor supports, or do what I had done on #1 and added a interior frame rail. Frame rail is what I call a 1"x2" or 2"x2" that runs along the interior walls. I feel this frame rail does three things on the exterior wall.

1. It supports the wall from inward forces.
2. It gives the wall a better bond to the floor. Making the glue work in shear in upward/downward forces.
3. It distributes what would be central forces across the floor.

I had left the frame rails out in the #2 build in hopes to keep the trailer light and simplify construction. It would probably do fine if the trailer was not intended to be used in off road conditions.

Also, after that trip I realized that that the 12" tires where worse than I had thought for this kind of travel. In a attempt to soften the ride more on the way out I lowered the tire pressure to 8lbs. Both tires rolled off the bead. The fix? Bigger wheels/tires. The largest wheel/tire I could go with the 4 lug hub was a ST175/80-13. That is a 13" wheel and tires that boost up from 20" to 24" diameter tire. I also had to use a 1" spacer to move the wheels away from the body. This does not sound like a big difference, but it made a huge difference for since the lager tires can absorb much more impact than the smaller tires. I was able to keep these tires a 20 psi on and off road for my next trip. This video opens up with me doing a short demonstration on how strong and light a foamie is, but then goes into the trip clips with the new tires and frame rails installed.



I have two big trips coming up next month. One in Northern Utah where we will be following the old Central Pacific Rail Road bed for 90 miles. Then it is over to central Oregon for the Geology Tour. Both trips should put the trailer through it's paces. In fact this weekend I am doing another trailer upgrade to prepare for these trips. In anticipation of extreme uneven roads I am having a 2"x2" steel tube installed that will run the length of the trailer and end at both sides with a Class 3 receiver tube. The front tube will allow me to switch out from a standard hitch to a pintle hitch. The rear tube will allow me to tow another trailer or install a receiver accessory such as a bike carrier. Also, a good extraction point. The tube will also strengthen the trailer since it will give significant strength to the trailers A frame from up/down forces. Also, being attached to all the trailers cross supports will spread pulling forces across the frame instead of at centralized locations on the A frame, which we already know is a weak point on HF trailers.

I post this up because I feel the foamie has some good points. It flexes enough to absorb hard impacts, but is rigid enough to stay together. I feel, with my limited use, that the foamie is/will be a superior trailer for off road service, in most cases. The main problem is that you have to treat a foamie as a foamie. You can't just bolt something to the side and expect it to stay there, unlike other trailers. But in turn, other trailers have to be stronger, which means heavier which in turn becomes a liability to off road use. So I suppose, as of right now, you have to determine what you can live with or without. In time I will be testing out different ideas I have to overcome these limitations. As of now I feel confident in my little foamies ability's.

Flex vs. stiffness. I think the foamie has the best of both of these worlds. With more testing we shall see.

[John61CT]

I plan for a very robust frame, so minimum flex forces on the foamie geometry.

Certainly not expecting the top five planes to help stabilize the bottom one.

But then the foamie pod will come off and the bottom frame needs to be robust enough for hauling boats and vehicles.

[tomhawk]

Now that winter has gone, I can move the car out of the garage and work on the trailer.

I am finishing the chassis and will need to purchase tires. I expect the trailer to be a simple foamie and ought to be light. I am concerned about the stiffness of the suspension. It makes sense that the the road shocks can damage the structures. Dancam thought his stiff suspension was trouble for his trailer.

I have a Dexter torflex #8 downrated to 800 lb. I think even this might be overkill unless I carry the usual 500 lb of beer. I plan to install some 13 inch tires.

I am confused about the choice of tires. Some trailer sites state that trailers should use ST tires that are typically inflated to 60 psi. I would think this is likely to give a rough ride. Lowering the inflation they say will decrease tire life.

The recommendations I have found expect that the trailer will weigh much more than a light foamie. I would think passenger auto tires with 30 psi inflation might be just fine and give a smoother ride.

Any thoughts on tires for a very light trailer? Is there a good place to read about this stuff?

Thanks,
Tom

[ghcoe]

Any thoughts on tires for a very light trailer? Is there a good place to read about this stuff?

Tire inflation ratings are based on the tires full load rating. Heat is what will destroy a tire and running a tire low with too much weight will cause it to prematurely fail. Side wall flex will heat the tire up and then failure. On the flip side running a tire at full psi with out full weight will cause the tread to wear funny. Usually the center tread will erase away before the sides will.

On a vehicle you will find a recommended tire inflation rating on the door. This will be close as long as the tires are similar and you can go with that weight to start. You watch the tread wear and if you notice that the center is wearing faster you know you need to deflate some. If the edges are wearing then you need to inflate some. Just a pound or two can make a difference.

The same is going to be for a trailer. For instance the HF trailer tires are rated at 50psi. I ran the tires on the freeway at 20psi with about 500lbs. The first few times I stopped I checked the tires to make sure they where not getting hot. Warm is ok, hot is not. I replace the original HF tires with a larger 13" tire rated at 50psi and still ran them at 20psi on a 800 mile trip with no issues. The idea is to keep the pressure to a point where you are applying the same amount of ground pressure along the full width of the tire. A little bit too much pressure you will wear the center tread, a bit too little and the edge tread will wear. Sometimes this is hard to tell here is a video to describe how to do a chalk test.

[GPW]

“ You have to sell people on a construction type not commonly known” … George , I feel your pain !!!! Imagine going to a wood and metal trailer forum as a stranger , and trying to convince them you can make a camper out of Foam … Bone 4 Tuna !!!

Acceleration = Mass X Speed … With less mass , foam has an advantage , those forces ( inertia /momentum ) that delaminated some sections might have destroyed a conventional trailer … We’ve seen those videos …

Yes , those drip edges sure are a blessing !!! ….